At one point some students studying E101 discovered that one could press ? and enter and the answer would be revealed. This feature was originally intended for tutors to use, as they could bring up a ? button on the interface somehow, but it functioned by the input field instead of making a direct call. This has now been fixed.

Additionally, since it's client-side Java it's not too hard to disassemble it to reveal the algorithm used to generate the problem, which is often sufficient information to work out the answer.